docs: def _setup_xauth(self):
          '''
          Set up the Xauthority file and the XAUTHORITY environment variable.
          '''
          handle, filename = tempfile.mkstemp(prefix='PyVirtualDisplay.',
                                              suffix='.Xauthority')
          self._xauth_filename = filename
          os.close(handle)
          # Save old environment
          self._old_xauth = {}
          self._old_xauth['AUTHFILE'] = os.getenv('AUTHFILE')
          self._old_xauth['XAUTHORITY'] = os.getenv('XAUTHORITY')
  
          os.environ['AUTHFILE'] = os.environ['XAUTHORITY'] = filename
          cookie = xauth.generate_mcookie()
          xauth.call('add', self.new_display_var, '.', cookie)